Conventional image sensors used for mobile application such as cell phone cameras use VCM actuators to adjust lens focus. The VCM actuator moves the lens closer or further from the image sensor to adjust focus, and is therefore large in size, mechanical, creates noise, and consumes a lot of power. Focusing can be slow with VCM actuator systems as the lens has to physically travel through the device. The VCM actuator uses an electric motor and gears, so naturally a large amount of power is consumed and the device is relatively noisy.
More recently, tunable lenses have been developed that can adjust the focal power or properties of the lens without physically moving any components (i.e. where the optical power of the lens is changed by applying an electric voltage or pulse to the lens). Optical power of a lens refers to the amount of focusing (e.g. convergence) that the lens imparts on light (or more specifically a light image) passing therethrough. An example of a tunable lens is tunable liquid crystal lens, which is a device in which a liquid crystal is employed to create the effect of a lens via electrical stimulus, and can be tuned to different optical powers by adjusting that electrical stimulus. A tunable liquid crystal lens achieves the effect of a lens by creating regions of differing indices of refraction in a liquid crystal when subjected to electrical stimulus. The tunable liquid crystal lens can be adjusted to different levels in a range of optical power by manipulating, for example, the voltages of the electrical signal applied to the lens. Tunable liquid crystal lenses consume less energy and can respond more quickly that those lenses with moving parts.
The present invention relates to the integration of a tunable liquid crystal lens with the image sensor package.